While we are on the topic of weight, we have a lot of questions from our patients about optimal weight gain during pregnancy. Let’s say we gain 30-32 lbs during the pregnancy. How is the weight distributed?
- Fetus: 7-8 lbs
- Maternal fat stores: 6-8 lbs
- Maternal blood volume: 3-4 lbs
- Maternal plasma volume: 2-3 lbs
- Amniotic fluid: 2 lbs
- Breast enlargement: 1-3 lbs
- Uterine enlargement: 2 lbs
- Placenta: 1.5 lbs
Now, how much weight gain is recommended? IOM (Institute of Medicine) has made these recommendations in order to achieve a baby at term that weighs 3000-4000gms. The recommendations are directly linked to our what our pre-pregnancy Body Mass Index (BMI) is. Click here to link to a BMI calculator.
Once, we’ve figured out our baseline BMI, here are the recommendations for maternal weight gain in women carrying one baby (women carrying twins should gain more weight and will be addressed at a later date):
- BMI <18 (underweight): gain 28-40 lbs
- BMI18.5-24.9 (normal): gain 25-35 lbs
- BMI 25-29 lbs (overweight): gain 15-25 lbs
- BMI>30 (obese): gain 11-20 lbs
What if we gain more weight than recommended? The concerns would be increased risk of c-section, increased risk of having a big baby, increased risk of weight retention after delivery, increased risk of the mother developing diabetes during and after pregnancy.
A few of us don’t gain enough weight. This may lead to a smaller baby which may increase that baby’s risk for heart disease and diabetes later in life.
Bottom line: If we are underweight or normal weight (BMI=24.9 or under), then gain about 1 pound a week in the second and third trimesters. If we are overweight or obese (BMI greater than 25), then gain about 1/2 pound a week in the second and third trimesters.